The disclosed invention is directed toward a device and a method for visually determining the relative elongation of a flexible member in tension or compression. The invention is applicable for setting the correct tension level in belts, preferably transmission belts. The disclosed device can be employed as either an integral part of the belting or a separate device for use with the belting.
When mounting a belt, or any other endless flexible article, between a leading member and a driven member, strict observation of the belt tension is required to permit full effectiveness while ensuring an optimal belt life. If the belt is too loose, it will slip and generate noise. If the belt is too tight, belt durability decreases and the associated members about which the belt travels are subjected to excessive stress. This is true for almost every type of belt in the automotive and manufacturing industries. Belts are normally adjusted, checked for tension, readjusted and rechecked until the proper belt tension is achieved.
Measuring belt tension has often been very difficult and time consuming. One known method of checking the mounting tension of a transmission belt requires special tooling which implies a delicate long procedure being needed to implement the belt. U.S. Pat. No. 4,860,597 discloses one such exemplary device.
Another method of correctly tensioning belts employs the measurement of the natural frequency of a vibrating span of the belt. The frequency of the vibrating belt span changes with tension. Expensive equipment is used to measure the change and the tension is subsequently calculated. Such known devices cost more than $1,000, proving to be a costly investment for those that need to purchase belt tension testers.
U.S. Pat. No. 5,391,120 discloses an elongation method for proper tensioning of a transmission belt. The belt is marked with two lines and a spacing requirement between the two lines. After installing the belt, the belt is elongated until the required spacing is met. After each adjustment to the belt tension, the separate measuring device is used to determine the spacing between the lines. This procedure of adjusting, stopping and measuring is repeated until the stated distance is achieved.
Other known methods include a deflection method whereby a known force is applied perpendicular to the center of a belt span and the belt deflected a certain distance.
Other non-belt-type application employ vernier scales for determining proper alignment. U.S. Pat. No. 5,385,289 discloses the use of vernier scales for alignment of a PC board and a solder stencil. The PC board has a set of etch blocks with a larger central block for denoting proper alignment when visible in the central opening of the solder stencil.
U.S. Pat. No. 4,185,908 discloses the use of a vernier belt tensioning system for a document feeder of a photocopy machine. Two sets of pitched vernier holes enable an accurate setting of the parallelness of the belt pulleys for the document feeder. When a set of holes are aligned in one set of plates for a first pulley, a pin is insert in the aligned holes. The corresponding set of plates for the second pulley is then adjusted until the same holes are aligned and a pin is inserted. The two sets of vernier scales enable the front and the back frames of the pulleys to be correctly aligned.
All of the aforementioned methods are either much more expensive than the disclosed invention or are much more cumbersome and time consuming. The disclosed invention provides a quick visual method of determining when the proper belt tension is reached. The disclosed invention also provides a xe2x80x9chands-freexe2x80x9d method of determining if proper belt tensioning has been achieved.
The present invention is directed toward a visual method of determining the relative elongation of a flexible member, when the member is in either tension or compression.
Another aspect of the present invention is to provide a simple and inexpensive means of measuring static strand tension in a member under tension or compression.
The present invention is achieved by an elongation measuring device affixed to belting that uses a visible vernier scale that greatly magnifies a small amount of elongation. The vernier scale is calibrated to correspond with the correct installation tension provided by the belt manufacturer.
The present method accomplishes measuring of the tension of a belt by attaching the device to the belt before tensioning of the belt, and watching for alignment of the scale until proper tension is achieved.